linux/net/sched/sch_qfq.c
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   1/*
   2 * net/sched/sch_qfq.c         Quick Fair Queueing Scheduler.
   3 *
   4 * Copyright (c) 2009 Fabio Checconi, Luigi Rizzo, and Paolo Valente.
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public License
   8 * version 2 as published by the Free Software Foundation.
   9 */
  10
  11#include <linux/module.h>
  12#include <linux/init.h>
  13#include <linux/bitops.h>
  14#include <linux/errno.h>
  15#include <linux/netdevice.h>
  16#include <linux/pkt_sched.h>
  17#include <net/sch_generic.h>
  18#include <net/pkt_sched.h>
  19#include <net/pkt_cls.h>
  20
  21
  22/*  Quick Fair Queueing
  23    ===================
  24
  25    Sources:
  26
  27    Fabio Checconi, Luigi Rizzo, and Paolo Valente: "QFQ: Efficient
  28    Packet Scheduling with Tight Bandwidth Distribution Guarantees."
  29
  30    See also:
  31    http://retis.sssup.it/~fabio/linux/qfq/
  32 */
  33
  34/*
  35
  36  Virtual time computations.
  37
  38  S, F and V are all computed in fixed point arithmetic with
  39  FRAC_BITS decimal bits.
  40
  41  QFQ_MAX_INDEX is the maximum index allowed for a group. We need
  42        one bit per index.
  43  QFQ_MAX_WSHIFT is the maximum power of two supported as a weight.
  44
  45  The layout of the bits is as below:
  46
  47                   [ MTU_SHIFT ][      FRAC_BITS    ]
  48                   [ MAX_INDEX    ][ MIN_SLOT_SHIFT ]
  49                                 ^.__grp->index = 0
  50                                 *.__grp->slot_shift
  51
  52  where MIN_SLOT_SHIFT is derived by difference from the others.
  53
  54  The max group index corresponds to Lmax/w_min, where
  55  Lmax=1<<MTU_SHIFT, w_min = 1 .
  56  From this, and knowing how many groups (MAX_INDEX) we want,
  57  we can derive the shift corresponding to each group.
  58
  59  Because we often need to compute
  60        F = S + len/w_i  and V = V + len/wsum
  61  instead of storing w_i store the value
  62        inv_w = (1<<FRAC_BITS)/w_i
  63  so we can do F = S + len * inv_w * wsum.
  64  We use W_TOT in the formulas so we can easily move between
  65  static and adaptive weight sum.
  66
  67  The per-scheduler-instance data contain all the data structures
  68  for the scheduler: bitmaps and bucket lists.
  69
  70 */
  71
  72/*
  73 * Maximum number of consecutive slots occupied by backlogged classes
  74 * inside a group.
  75 */
  76#define QFQ_MAX_SLOTS   32
  77
  78/*
  79 * Shifts used for class<->group mapping.  We allow class weights that are
  80 * in the range [1, 2^MAX_WSHIFT], and we try to map each class i to the
  81 * group with the smallest index that can support the L_i / r_i configured
  82 * for the class.
  83 *
  84 * grp->index is the index of the group; and grp->slot_shift
  85 * is the shift for the corresponding (scaled) sigma_i.
  86 */
  87#define QFQ_MAX_INDEX           19
  88#define QFQ_MAX_WSHIFT          16
  89
  90#define QFQ_MAX_WEIGHT          (1<<QFQ_MAX_WSHIFT)
  91#define QFQ_MAX_WSUM            (2*QFQ_MAX_WEIGHT)
  92
  93#define FRAC_BITS               30      /* fixed point arithmetic */
  94#define ONE_FP                  (1UL << FRAC_BITS)
  95#define IWSUM                   (ONE_FP/QFQ_MAX_WSUM)
  96
  97#define QFQ_MTU_SHIFT           11
  98#define QFQ_MIN_SLOT_SHIFT      (FRAC_BITS + QFQ_MTU_SHIFT - QFQ_MAX_INDEX)
  99
 100/*
 101 * Possible group states.  These values are used as indexes for the bitmaps
 102 * array of struct qfq_queue.
 103 */
 104enum qfq_state { ER, IR, EB, IB, QFQ_MAX_STATE };
 105
 106struct qfq_group;
 107
 108struct qfq_class {
 109        struct Qdisc_class_common common;
 110
 111        unsigned int refcnt;
 112        unsigned int filter_cnt;
 113
 114        struct gnet_stats_basic_packed bstats;
 115        struct gnet_stats_queue qstats;
 116        struct gnet_stats_rate_est rate_est;
 117        struct Qdisc *qdisc;
 118
 119        struct hlist_node next; /* Link for the slot list. */
 120        u64 S, F;               /* flow timestamps (exact) */
 121
 122        /* group we belong to. In principle we would need the index,
 123         * which is log_2(lmax/weight), but we never reference it
 124         * directly, only the group.
 125         */
 126        struct qfq_group *grp;
 127
 128        /* these are copied from the flowset. */
 129        u32     inv_w;          /* ONE_FP/weight */
 130        u32     lmax;           /* Max packet size for this flow. */
 131};
 132
 133struct qfq_group {
 134        u64 S, F;                       /* group timestamps (approx). */
 135        unsigned int slot_shift;        /* Slot shift. */
 136        unsigned int index;             /* Group index. */
 137        unsigned int front;             /* Index of the front slot. */
 138        unsigned long full_slots;       /* non-empty slots */
 139
 140        /* Array of RR lists of active classes. */
 141        struct hlist_head slots[QFQ_MAX_SLOTS];
 142};
 143
 144struct qfq_sched {
 145        struct tcf_proto *filter_list;
 146        struct Qdisc_class_hash clhash;
 147
 148        u64             V;              /* Precise virtual time. */
 149        u32             wsum;           /* weight sum */
 150
 151        unsigned long bitmaps[QFQ_MAX_STATE];       /* Group bitmaps. */
 152        struct qfq_group groups[QFQ_MAX_INDEX + 1]; /* The groups. */
 153};
 154
 155static struct qfq_class *qfq_find_class(struct Qdisc *sch, u32 classid)
 156{
 157        struct qfq_sched *q = qdisc_priv(sch);
 158        struct Qdisc_class_common *clc;
 159
 160        clc = qdisc_class_find(&q->clhash, classid);
 161        if (clc == NULL)
 162                return NULL;
 163        return container_of(clc, struct qfq_class, common);
 164}
 165
 166static void qfq_purge_queue(struct qfq_class *cl)
 167{
 168        unsigned int len = cl->qdisc->q.qlen;
 169
 170        qdisc_reset(cl->qdisc);
 171        qdisc_tree_decrease_qlen(cl->qdisc, len);
 172}
 173
 174static const struct nla_policy qfq_policy[TCA_QFQ_MAX + 1] = {
 175        [TCA_QFQ_WEIGHT] = { .type = NLA_U32 },
 176        [TCA_QFQ_LMAX] = { .type = NLA_U32 },
 177};
 178
 179/*
 180 * Calculate a flow index, given its weight and maximum packet length.
 181 * index = log_2(maxlen/weight) but we need to apply the scaling.
 182 * This is used only once at flow creation.
 183 */
 184static int qfq_calc_index(u32 inv_w, unsigned int maxlen)
 185{
 186        u64 slot_size = (u64)maxlen * inv_w;
 187        unsigned long size_map;
 188        int index = 0;
 189
 190        size_map = slot_size >> QFQ_MIN_SLOT_SHIFT;
 191        if (!size_map)
 192                goto out;
 193
 194        index = __fls(size_map) + 1;    /* basically a log_2 */
 195        index -= !(slot_size - (1ULL << (index + QFQ_MIN_SLOT_SHIFT - 1)));
 196
 197        if (index < 0)
 198                index = 0;
 199out:
 200        pr_debug("qfq calc_index: W = %lu, L = %u, I = %d\n",
 201                 (unsigned long) ONE_FP/inv_w, maxlen, index);
 202
 203        return index;
 204}
 205
 206/* Length of the next packet (0 if the queue is empty). */
 207static unsigned int qdisc_peek_len(struct Qdisc *sch)
 208{
 209        struct sk_buff *skb;
 210
 211        skb = sch->ops->peek(sch);
 212        return skb ? qdisc_pkt_len(skb) : 0;
 213}
 214
 215static void qfq_deactivate_class(struct qfq_sched *, struct qfq_class *);
 216static void qfq_activate_class(struct qfq_sched *q, struct qfq_class *cl,
 217                               unsigned int len);
 218
 219static void qfq_update_class_params(struct qfq_sched *q, struct qfq_class *cl,
 220                                    u32 lmax, u32 inv_w, int delta_w)
 221{
 222        int i;
 223
 224        /* update qfq-specific data */
 225        cl->lmax = lmax;
 226        cl->inv_w = inv_w;
 227        i = qfq_calc_index(cl->inv_w, cl->lmax);
 228
 229        cl->grp = &q->groups[i];
 230
 231        q->wsum += delta_w;
 232}
 233
 234static int qfq_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 235                            struct nlattr **tca, unsigned long *arg)
 236{
 237        struct qfq_sched *q = qdisc_priv(sch);
 238        struct qfq_class *cl = (struct qfq_class *)*arg;
 239        struct nlattr *tb[TCA_QFQ_MAX + 1];
 240        u32 weight, lmax, inv_w;
 241        int i, err;
 242        int delta_w;
 243
 244        if (tca[TCA_OPTIONS] == NULL) {
 245                pr_notice("qfq: no options\n");
 246                return -EINVAL;
 247        }
 248
 249        err = nla_parse_nested(tb, TCA_QFQ_MAX, tca[TCA_OPTIONS], qfq_policy);
 250        if (err < 0)
 251                return err;
 252
 253        if (tb[TCA_QFQ_WEIGHT]) {
 254                weight = nla_get_u32(tb[TCA_QFQ_WEIGHT]);
 255                if (!weight || weight > (1UL << QFQ_MAX_WSHIFT)) {
 256                        pr_notice("qfq: invalid weight %u\n", weight);
 257                        return -EINVAL;
 258                }
 259        } else
 260                weight = 1;
 261
 262        inv_w = ONE_FP / weight;
 263        weight = ONE_FP / inv_w;
 264        delta_w = weight - (cl ? ONE_FP / cl->inv_w : 0);
 265        if (q->wsum + delta_w > QFQ_MAX_WSUM) {
 266                pr_notice("qfq: total weight out of range (%u + %u)\n",
 267                          delta_w, q->wsum);
 268                return -EINVAL;
 269        }
 270
 271        if (tb[TCA_QFQ_LMAX]) {
 272                lmax = nla_get_u32(tb[TCA_QFQ_LMAX]);
 273                if (!lmax || lmax > (1UL << QFQ_MTU_SHIFT)) {
 274                        pr_notice("qfq: invalid max length %u\n", lmax);
 275                        return -EINVAL;
 276                }
 277        } else
 278                lmax = 1UL << QFQ_MTU_SHIFT;
 279
 280        if (cl != NULL) {
 281                bool need_reactivation = false;
 282
 283                if (tca[TCA_RATE]) {
 284                        err = gen_replace_estimator(&cl->bstats, &cl->rate_est,
 285                                                    qdisc_root_sleeping_lock(sch),
 286                                                    tca[TCA_RATE]);
 287                        if (err)
 288                                return err;
 289                }
 290
 291                if (lmax == cl->lmax && inv_w == cl->inv_w)
 292                        return 0; /* nothing to update */
 293
 294                i = qfq_calc_index(inv_w, lmax);
 295                sch_tree_lock(sch);
 296                if (&q->groups[i] != cl->grp && cl->qdisc->q.qlen > 0) {
 297                        /*
 298                         * shift cl->F back, to not charge the
 299                         * class for the not-yet-served head
 300                         * packet
 301                         */
 302                        cl->F = cl->S;
 303                        /* remove class from its slot in the old group */
 304                        qfq_deactivate_class(q, cl);
 305                        need_reactivation = true;
 306                }
 307
 308                qfq_update_class_params(q, cl, lmax, inv_w, delta_w);
 309
 310                if (need_reactivation) /* activate in new group */
 311                        qfq_activate_class(q, cl, qdisc_peek_len(cl->qdisc));
 312                sch_tree_unlock(sch);
 313
 314                return 0;
 315        }
 316
 317        cl = kzalloc(sizeof(struct qfq_class), GFP_KERNEL);
 318        if (cl == NULL)
 319                return -ENOBUFS;
 320
 321        cl->refcnt = 1;
 322        cl->common.classid = classid;
 323
 324        qfq_update_class_params(q, cl, lmax, inv_w, delta_w);
 325
 326        cl->qdisc = qdisc_create_dflt(sch->dev_queue,
 327                                      &pfifo_qdisc_ops, classid);
 328        if (cl->qdisc == NULL)
 329                cl->qdisc = &noop_qdisc;
 330
 331        if (tca[TCA_RATE]) {
 332                err = gen_new_estimator(&cl->bstats, &cl->rate_est,
 333                                        qdisc_root_sleeping_lock(sch),
 334                                        tca[TCA_RATE]);
 335                if (err) {
 336                        qdisc_destroy(cl->qdisc);
 337                        kfree(cl);
 338                        return err;
 339                }
 340        }
 341
 342        sch_tree_lock(sch);
 343        qdisc_class_hash_insert(&q->clhash, &cl->common);
 344        sch_tree_unlock(sch);
 345
 346        qdisc_class_hash_grow(sch, &q->clhash);
 347
 348        *arg = (unsigned long)cl;
 349        return 0;
 350}
 351
 352static void qfq_destroy_class(struct Qdisc *sch, struct qfq_class *cl)
 353{
 354        struct qfq_sched *q = qdisc_priv(sch);
 355
 356        if (cl->inv_w) {
 357                q->wsum -= ONE_FP / cl->inv_w;
 358                cl->inv_w = 0;
 359        }
 360
 361        gen_kill_estimator(&cl->bstats, &cl->rate_est);
 362        qdisc_destroy(cl->qdisc);
 363        kfree(cl);
 364}
 365
 366static int qfq_delete_class(struct Qdisc *sch, unsigned long arg)
 367{
 368        struct qfq_sched *q = qdisc_priv(sch);
 369        struct qfq_class *cl = (struct qfq_class *)arg;
 370
 371        if (cl->filter_cnt > 0)
 372                return -EBUSY;
 373
 374        sch_tree_lock(sch);
 375
 376        qfq_purge_queue(cl);
 377        qdisc_class_hash_remove(&q->clhash, &cl->common);
 378
 379        BUG_ON(--cl->refcnt == 0);
 380        /*
 381         * This shouldn't happen: we "hold" one cops->get() when called
 382         * from tc_ctl_tclass; the destroy method is done from cops->put().
 383         */
 384
 385        sch_tree_unlock(sch);
 386        return 0;
 387}
 388
 389static unsigned long qfq_get_class(struct Qdisc *sch, u32 classid)
 390{
 391        struct qfq_class *cl = qfq_find_class(sch, classid);
 392
 393        if (cl != NULL)
 394                cl->refcnt++;
 395
 396        return (unsigned long)cl;
 397}
 398
 399static void qfq_put_class(struct Qdisc *sch, unsigned long arg)
 400{
 401        struct qfq_class *cl = (struct qfq_class *)arg;
 402
 403        if (--cl->refcnt == 0)
 404                qfq_destroy_class(sch, cl);
 405}
 406
 407static struct tcf_proto **qfq_tcf_chain(struct Qdisc *sch, unsigned long cl)
 408{
 409        struct qfq_sched *q = qdisc_priv(sch);
 410
 411        if (cl)
 412                return NULL;
 413
 414        return &q->filter_list;
 415}
 416
 417static unsigned long qfq_bind_tcf(struct Qdisc *sch, unsigned long parent,
 418                                  u32 classid)
 419{
 420        struct qfq_class *cl = qfq_find_class(sch, classid);
 421
 422        if (cl != NULL)
 423                cl->filter_cnt++;
 424
 425        return (unsigned long)cl;
 426}
 427
 428static void qfq_unbind_tcf(struct Qdisc *sch, unsigned long arg)
 429{
 430        struct qfq_class *cl = (struct qfq_class *)arg;
 431
 432        cl->filter_cnt--;
 433}
 434
 435static int qfq_graft_class(struct Qdisc *sch, unsigned long arg,
 436                           struct Qdisc *new, struct Qdisc **old)
 437{
 438        struct qfq_class *cl = (struct qfq_class *)arg;
 439
 440        if (new == NULL) {
 441                new = qdisc_create_dflt(sch->dev_queue,
 442                                        &pfifo_qdisc_ops, cl->common.classid);
 443                if (new == NULL)
 444                        new = &noop_qdisc;
 445        }
 446
 447        sch_tree_lock(sch);
 448        qfq_purge_queue(cl);
 449        *old = cl->qdisc;
 450        cl->qdisc = new;
 451        sch_tree_unlock(sch);
 452        return 0;
 453}
 454
 455static struct Qdisc *qfq_class_leaf(struct Qdisc *sch, unsigned long arg)
 456{
 457        struct qfq_class *cl = (struct qfq_class *)arg;
 458
 459        return cl->qdisc;
 460}
 461
 462static int qfq_dump_class(struct Qdisc *sch, unsigned long arg,
 463                          struct sk_buff *skb, struct tcmsg *tcm)
 464{
 465        struct qfq_class *cl = (struct qfq_class *)arg;
 466        struct nlattr *nest;
 467
 468        tcm->tcm_parent = TC_H_ROOT;
 469        tcm->tcm_handle = cl->common.classid;
 470        tcm->tcm_info   = cl->qdisc->handle;
 471
 472        nest = nla_nest_start(skb, TCA_OPTIONS);
 473        if (nest == NULL)
 474                goto nla_put_failure;
 475        if (nla_put_u32(skb, TCA_QFQ_WEIGHT, ONE_FP/cl->inv_w) ||
 476            nla_put_u32(skb, TCA_QFQ_LMAX, cl->lmax))
 477                goto nla_put_failure;
 478        return nla_nest_end(skb, nest);
 479
 480nla_put_failure:
 481        nla_nest_cancel(skb, nest);
 482        return -EMSGSIZE;
 483}
 484
 485static int qfq_dump_class_stats(struct Qdisc *sch, unsigned long arg,
 486                                struct gnet_dump *d)
 487{
 488        struct qfq_class *cl = (struct qfq_class *)arg;
 489        struct tc_qfq_stats xstats;
 490
 491        memset(&xstats, 0, sizeof(xstats));
 492        cl->qdisc->qstats.qlen = cl->qdisc->q.qlen;
 493
 494        xstats.weight = ONE_FP/cl->inv_w;
 495        xstats.lmax = cl->lmax;
 496
 497        if (gnet_stats_copy_basic(d, &cl->bstats) < 0 ||
 498            gnet_stats_copy_rate_est(d, &cl->bstats, &cl->rate_est) < 0 ||
 499            gnet_stats_copy_queue(d, &cl->qdisc->qstats) < 0)
 500                return -1;
 501
 502        return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
 503}
 504
 505static void qfq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
 506{
 507        struct qfq_sched *q = qdisc_priv(sch);
 508        struct qfq_class *cl;
 509        struct hlist_node *n;
 510        unsigned int i;
 511
 512        if (arg->stop)
 513                return;
 514
 515        for (i = 0; i < q->clhash.hashsize; i++) {
 516                hlist_for_each_entry(cl, n, &q->clhash.hash[i], common.hnode) {
 517                        if (arg->count < arg->skip) {
 518                                arg->count++;
 519                                continue;
 520                        }
 521                        if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
 522                                arg->stop = 1;
 523                                return;
 524                        }
 525                        arg->count++;
 526                }
 527        }
 528}
 529
 530static struct qfq_class *qfq_classify(struct sk_buff *skb, struct Qdisc *sch,
 531                                      int *qerr)
 532{
 533        struct qfq_sched *q = qdisc_priv(sch);
 534        struct qfq_class *cl;
 535        struct tcf_result res;
 536        int result;
 537
 538        if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
 539                pr_debug("qfq_classify: found %d\n", skb->priority);
 540                cl = qfq_find_class(sch, skb->priority);
 541                if (cl != NULL)
 542                        return cl;
 543        }
 544
 545        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
 546        result = tc_classify(skb, q->filter_list, &res);
 547        if (result >= 0) {
 548#ifdef CONFIG_NET_CLS_ACT
 549                switch (result) {
 550                case TC_ACT_QUEUED:
 551                case TC_ACT_STOLEN:
 552                        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
 553                case TC_ACT_SHOT:
 554                        return NULL;
 555                }
 556#endif
 557                cl = (struct qfq_class *)res.class;
 558                if (cl == NULL)
 559                        cl = qfq_find_class(sch, res.classid);
 560                return cl;
 561        }
 562
 563        return NULL;
 564}
 565
 566/* Generic comparison function, handling wraparound. */
 567static inline int qfq_gt(u64 a, u64 b)
 568{
 569        return (s64)(a - b) > 0;
 570}
 571
 572/* Round a precise timestamp to its slotted value. */
 573static inline u64 qfq_round_down(u64 ts, unsigned int shift)
 574{
 575        return ts & ~((1ULL << shift) - 1);
 576}
 577
 578/* return the pointer to the group with lowest index in the bitmap */
 579static inline struct qfq_group *qfq_ffs(struct qfq_sched *q,
 580                                        unsigned long bitmap)
 581{
 582        int index = __ffs(bitmap);
 583        return &q->groups[index];
 584}
 585/* Calculate a mask to mimic what would be ffs_from(). */
 586static inline unsigned long mask_from(unsigned long bitmap, int from)
 587{
 588        return bitmap & ~((1UL << from) - 1);
 589}
 590
 591/*
 592 * The state computation relies on ER=0, IR=1, EB=2, IB=3
 593 * First compute eligibility comparing grp->S, q->V,
 594 * then check if someone is blocking us and possibly add EB
 595 */
 596static int qfq_calc_state(struct qfq_sched *q, const struct qfq_group *grp)
 597{
 598        /* if S > V we are not eligible */
 599        unsigned int state = qfq_gt(grp->S, q->V);
 600        unsigned long mask = mask_from(q->bitmaps[ER], grp->index);
 601        struct qfq_group *next;
 602
 603        if (mask) {
 604                next = qfq_ffs(q, mask);
 605                if (qfq_gt(grp->F, next->F))
 606                        state |= EB;
 607        }
 608
 609        return state;
 610}
 611
 612
 613/*
 614 * In principle
 615 *      q->bitmaps[dst] |= q->bitmaps[src] & mask;
 616 *      q->bitmaps[src] &= ~mask;
 617 * but we should make sure that src != dst
 618 */
 619static inline void qfq_move_groups(struct qfq_sched *q, unsigned long mask,
 620                                   int src, int dst)
 621{
 622        q->bitmaps[dst] |= q->bitmaps[src] & mask;
 623        q->bitmaps[src] &= ~mask;
 624}
 625
 626static void qfq_unblock_groups(struct qfq_sched *q, int index, u64 old_F)
 627{
 628        unsigned long mask = mask_from(q->bitmaps[ER], index + 1);
 629        struct qfq_group *next;
 630
 631        if (mask) {
 632                next = qfq_ffs(q, mask);
 633                if (!qfq_gt(next->F, old_F))
 634                        return;
 635        }
 636
 637        mask = (1UL << index) - 1;
 638        qfq_move_groups(q, mask, EB, ER);
 639        qfq_move_groups(q, mask, IB, IR);
 640}
 641
 642/*
 643 * perhaps
 644 *
 645        old_V ^= q->V;
 646        old_V >>= QFQ_MIN_SLOT_SHIFT;
 647        if (old_V) {
 648                ...
 649        }
 650 *
 651 */
 652static void qfq_make_eligible(struct qfq_sched *q, u64 old_V)
 653{
 654        unsigned long vslot = q->V >> QFQ_MIN_SLOT_SHIFT;
 655        unsigned long old_vslot = old_V >> QFQ_MIN_SLOT_SHIFT;
 656
 657        if (vslot != old_vslot) {
 658                unsigned long mask = (1UL << fls(vslot ^ old_vslot)) - 1;
 659                qfq_move_groups(q, mask, IR, ER);
 660                qfq_move_groups(q, mask, IB, EB);
 661        }
 662}
 663
 664
 665/*
 666 * XXX we should make sure that slot becomes less than 32.
 667 * This is guaranteed by the input values.
 668 * roundedS is always cl->S rounded on grp->slot_shift bits.
 669 */
 670static void qfq_slot_insert(struct qfq_group *grp, struct qfq_class *cl,
 671                            u64 roundedS)
 672{
 673        u64 slot = (roundedS - grp->S) >> grp->slot_shift;
 674        unsigned int i = (grp->front + slot) % QFQ_MAX_SLOTS;
 675
 676        hlist_add_head(&cl->next, &grp->slots[i]);
 677        __set_bit(slot, &grp->full_slots);
 678}
 679
 680/* Maybe introduce hlist_first_entry?? */
 681static struct qfq_class *qfq_slot_head(struct qfq_group *grp)
 682{
 683        return hlist_entry(grp->slots[grp->front].first,
 684                           struct qfq_class, next);
 685}
 686
 687/*
 688 * remove the entry from the slot
 689 */
 690static void qfq_front_slot_remove(struct qfq_group *grp)
 691{
 692        struct qfq_class *cl = qfq_slot_head(grp);
 693
 694        BUG_ON(!cl);
 695        hlist_del(&cl->next);
 696        if (hlist_empty(&grp->slots[grp->front]))
 697                __clear_bit(0, &grp->full_slots);
 698}
 699
 700/*
 701 * Returns the first full queue in a group. As a side effect,
 702 * adjust the bucket list so the first non-empty bucket is at
 703 * position 0 in full_slots.
 704 */
 705static struct qfq_class *qfq_slot_scan(struct qfq_group *grp)
 706{
 707        unsigned int i;
 708
 709        pr_debug("qfq slot_scan: grp %u full %#lx\n",
 710                 grp->index, grp->full_slots);
 711
 712        if (grp->full_slots == 0)
 713                return NULL;
 714
 715        i = __ffs(grp->full_slots);  /* zero based */
 716        if (i > 0) {
 717                grp->front = (grp->front + i) % QFQ_MAX_SLOTS;
 718                grp->full_slots >>= i;
 719        }
 720
 721        return qfq_slot_head(grp);
 722}
 723
 724/*
 725 * adjust the bucket list. When the start time of a group decreases,
 726 * we move the index down (modulo QFQ_MAX_SLOTS) so we don't need to
 727 * move the objects. The mask of occupied slots must be shifted
 728 * because we use ffs() to find the first non-empty slot.
 729 * This covers decreases in the group's start time, but what about
 730 * increases of the start time ?
 731 * Here too we should make sure that i is less than 32
 732 */
 733static void qfq_slot_rotate(struct qfq_group *grp, u64 roundedS)
 734{
 735        unsigned int i = (grp->S - roundedS) >> grp->slot_shift;
 736
 737        grp->full_slots <<= i;
 738        grp->front = (grp->front - i) % QFQ_MAX_SLOTS;
 739}
 740
 741static void qfq_update_eligible(struct qfq_sched *q, u64 old_V)
 742{
 743        struct qfq_group *grp;
 744        unsigned long ineligible;
 745
 746        ineligible = q->bitmaps[IR] | q->bitmaps[IB];
 747        if (ineligible) {
 748                if (!q->bitmaps[ER]) {
 749                        grp = qfq_ffs(q, ineligible);
 750                        if (qfq_gt(grp->S, q->V))
 751                                q->V = grp->S;
 752                }
 753                qfq_make_eligible(q, old_V);
 754        }
 755}
 756
 757/*
 758 * Updates the class, returns true if also the group needs to be updated.
 759 */
 760static bool qfq_update_class(struct qfq_group *grp, struct qfq_class *cl)
 761{
 762        unsigned int len = qdisc_peek_len(cl->qdisc);
 763
 764        cl->S = cl->F;
 765        if (!len)
 766                qfq_front_slot_remove(grp);     /* queue is empty */
 767        else {
 768                u64 roundedS;
 769
 770                cl->F = cl->S + (u64)len * cl->inv_w;
 771                roundedS = qfq_round_down(cl->S, grp->slot_shift);
 772                if (roundedS == grp->S)
 773                        return false;
 774
 775                qfq_front_slot_remove(grp);
 776                qfq_slot_insert(grp, cl, roundedS);
 777        }
 778
 779        return true;
 780}
 781
 782static struct sk_buff *qfq_dequeue(struct Qdisc *sch)
 783{
 784        struct qfq_sched *q = qdisc_priv(sch);
 785        struct qfq_group *grp;
 786        struct qfq_class *cl;
 787        struct sk_buff *skb;
 788        unsigned int len;
 789        u64 old_V;
 790
 791        if (!q->bitmaps[ER])
 792                return NULL;
 793
 794        grp = qfq_ffs(q, q->bitmaps[ER]);
 795
 796        cl = qfq_slot_head(grp);
 797        skb = qdisc_dequeue_peeked(cl->qdisc);
 798        if (!skb) {
 799                WARN_ONCE(1, "qfq_dequeue: non-workconserving leaf\n");
 800                return NULL;
 801        }
 802
 803        sch->q.qlen--;
 804        qdisc_bstats_update(sch, skb);
 805
 806        old_V = q->V;
 807        len = qdisc_pkt_len(skb);
 808        q->V += (u64)len * IWSUM;
 809        pr_debug("qfq dequeue: len %u F %lld now %lld\n",
 810                 len, (unsigned long long) cl->F, (unsigned long long) q->V);
 811
 812        if (qfq_update_class(grp, cl)) {
 813                u64 old_F = grp->F;
 814
 815                cl = qfq_slot_scan(grp);
 816                if (!cl)
 817                        __clear_bit(grp->index, &q->bitmaps[ER]);
 818                else {
 819                        u64 roundedS = qfq_round_down(cl->S, grp->slot_shift);
 820                        unsigned int s;
 821
 822                        if (grp->S == roundedS)
 823                                goto skip_unblock;
 824                        grp->S = roundedS;
 825                        grp->F = roundedS + (2ULL << grp->slot_shift);
 826                        __clear_bit(grp->index, &q->bitmaps[ER]);
 827                        s = qfq_calc_state(q, grp);
 828                        __set_bit(grp->index, &q->bitmaps[s]);
 829                }
 830
 831                qfq_unblock_groups(q, grp->index, old_F);
 832        }
 833
 834skip_unblock:
 835        qfq_update_eligible(q, old_V);
 836
 837        return skb;
 838}
 839
 840/*
 841 * Assign a reasonable start time for a new flow k in group i.
 842 * Admissible values for \hat(F) are multiples of \sigma_i
 843 * no greater than V+\sigma_i . Larger values mean that
 844 * we had a wraparound so we consider the timestamp to be stale.
 845 *
 846 * If F is not stale and F >= V then we set S = F.
 847 * Otherwise we should assign S = V, but this may violate
 848 * the ordering in ER. So, if we have groups in ER, set S to
 849 * the F_j of the first group j which would be blocking us.
 850 * We are guaranteed not to move S backward because
 851 * otherwise our group i would still be blocked.
 852 */
 853static void qfq_update_start(struct qfq_sched *q, struct qfq_class *cl)
 854{
 855        unsigned long mask;
 856        u64 limit, roundedF;
 857        int slot_shift = cl->grp->slot_shift;
 858
 859        roundedF = qfq_round_down(cl->F, slot_shift);
 860        limit = qfq_round_down(q->V, slot_shift) + (1ULL << slot_shift);
 861
 862        if (!qfq_gt(cl->F, q->V) || qfq_gt(roundedF, limit)) {
 863                /* timestamp was stale */
 864                mask = mask_from(q->bitmaps[ER], cl->grp->index);
 865                if (mask) {
 866                        struct qfq_group *next = qfq_ffs(q, mask);
 867                        if (qfq_gt(roundedF, next->F)) {
 868                                if (qfq_gt(limit, next->F))
 869                                        cl->S = next->F;
 870                                else /* preserve timestamp correctness */
 871                                        cl->S = limit;
 872                                return;
 873                        }
 874                }
 875                cl->S = q->V;
 876        } else  /* timestamp is not stale */
 877                cl->S = cl->F;
 878}
 879
 880static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 881{
 882        struct qfq_sched *q = qdisc_priv(sch);
 883        struct qfq_class *cl;
 884        int err;
 885
 886        cl = qfq_classify(skb, sch, &err);
 887        if (cl == NULL) {
 888                if (err & __NET_XMIT_BYPASS)
 889                        sch->qstats.drops++;
 890                kfree_skb(skb);
 891                return err;
 892        }
 893        pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid);
 894
 895        err = qdisc_enqueue(skb, cl->qdisc);
 896        if (unlikely(err != NET_XMIT_SUCCESS)) {
 897                pr_debug("qfq_enqueue: enqueue failed %d\n", err);
 898                if (net_xmit_drop_count(err)) {
 899                        cl->qstats.drops++;
 900                        sch->qstats.drops++;
 901                }
 902                return err;
 903        }
 904
 905        bstats_update(&cl->bstats, skb);
 906        ++sch->q.qlen;
 907
 908        /* If the new skb is not the head of queue, then done here. */
 909        if (cl->qdisc->q.qlen != 1)
 910                return err;
 911
 912        /* If reach this point, queue q was idle */
 913        qfq_activate_class(q, cl, qdisc_pkt_len(skb));
 914
 915        return err;
 916}
 917
 918/*
 919 * Handle class switch from idle to backlogged.
 920 */
 921static void qfq_activate_class(struct qfq_sched *q, struct qfq_class *cl,
 922                               unsigned int pkt_len)
 923{
 924        struct qfq_group *grp = cl->grp;
 925        u64 roundedS;
 926        int s;
 927
 928        qfq_update_start(q, cl);
 929
 930        /* compute new finish time and rounded start. */
 931        cl->F = cl->S + (u64)pkt_len * cl->inv_w;
 932        roundedS = qfq_round_down(cl->S, grp->slot_shift);
 933
 934        /*
 935         * insert cl in the correct bucket.
 936         * If cl->S >= grp->S we don't need to adjust the
 937         * bucket list and simply go to the insertion phase.
 938         * Otherwise grp->S is decreasing, we must make room
 939         * in the bucket list, and also recompute the group state.
 940         * Finally, if there were no flows in this group and nobody
 941         * was in ER make sure to adjust V.
 942         */
 943        if (grp->full_slots) {
 944                if (!qfq_gt(grp->S, cl->S))
 945                        goto skip_update;
 946
 947                /* create a slot for this cl->S */
 948                qfq_slot_rotate(grp, roundedS);
 949                /* group was surely ineligible, remove */
 950                __clear_bit(grp->index, &q->bitmaps[IR]);
 951                __clear_bit(grp->index, &q->bitmaps[IB]);
 952        } else if (!q->bitmaps[ER] && qfq_gt(roundedS, q->V))
 953                q->V = roundedS;
 954
 955        grp->S = roundedS;
 956        grp->F = roundedS + (2ULL << grp->slot_shift);
 957        s = qfq_calc_state(q, grp);
 958        __set_bit(grp->index, &q->bitmaps[s]);
 959
 960        pr_debug("qfq enqueue: new state %d %#lx S %lld F %lld V %lld\n",
 961                 s, q->bitmaps[s],
 962                 (unsigned long long) cl->S,
 963                 (unsigned long long) cl->F,
 964                 (unsigned long long) q->V);
 965
 966skip_update:
 967        qfq_slot_insert(grp, cl, roundedS);
 968}
 969
 970
 971static void qfq_slot_remove(struct qfq_sched *q, struct qfq_group *grp,
 972                            struct qfq_class *cl)
 973{
 974        unsigned int i, offset;
 975        u64 roundedS;
 976
 977        roundedS = qfq_round_down(cl->S, grp->slot_shift);
 978        offset = (roundedS - grp->S) >> grp->slot_shift;
 979        i = (grp->front + offset) % QFQ_MAX_SLOTS;
 980
 981        hlist_del(&cl->next);
 982        if (hlist_empty(&grp->slots[i]))
 983                __clear_bit(offset, &grp->full_slots);
 984}
 985
 986/*
 987 * called to forcibly destroy a queue.
 988 * If the queue is not in the front bucket, or if it has
 989 * other queues in the front bucket, we can simply remove
 990 * the queue with no other side effects.
 991 * Otherwise we must propagate the event up.
 992 */
 993static void qfq_deactivate_class(struct qfq_sched *q, struct qfq_class *cl)
 994{
 995        struct qfq_group *grp = cl->grp;
 996        unsigned long mask;
 997        u64 roundedS;
 998        int s;
 999
1000        cl->F = cl->S;
1001        qfq_slot_remove(q, grp, cl);
1002
1003        if (!grp->full_slots) {
1004                __clear_bit(grp->index, &q->bitmaps[IR]);
1005                __clear_bit(grp->index, &q->bitmaps[EB]);
1006                __clear_bit(grp->index, &q->bitmaps[IB]);
1007
1008                if (test_bit(grp->index, &q->bitmaps[ER]) &&
1009                    !(q->bitmaps[ER] & ~((1UL << grp->index) - 1))) {
1010                        mask = q->bitmaps[ER] & ((1UL << grp->index) - 1);
1011                        if (mask)
1012                                mask = ~((1UL << __fls(mask)) - 1);
1013                        else
1014                                mask = ~0UL;
1015                        qfq_move_groups(q, mask, EB, ER);
1016                        qfq_move_groups(q, mask, IB, IR);
1017                }
1018                __clear_bit(grp->index, &q->bitmaps[ER]);
1019        } else if (hlist_empty(&grp->slots[grp->front])) {
1020                cl = qfq_slot_scan(grp);
1021                roundedS = qfq_round_down(cl->S, grp->slot_shift);
1022                if (grp->S != roundedS) {
1023                        __clear_bit(grp->index, &q->bitmaps[ER]);
1024                        __clear_bit(grp->index, &q->bitmaps[IR]);
1025                        __clear_bit(grp->index, &q->bitmaps[EB]);
1026                        __clear_bit(grp->index, &q->bitmaps[IB]);
1027                        grp->S = roundedS;
1028                        grp->F = roundedS + (2ULL << grp->slot_shift);
1029                        s = qfq_calc_state(q, grp);
1030                        __set_bit(grp->index, &q->bitmaps[s]);
1031                }
1032        }
1033
1034        qfq_update_eligible(q, q->V);
1035}
1036
1037static void qfq_qlen_notify(struct Qdisc *sch, unsigned long arg)
1038{
1039        struct qfq_sched *q = qdisc_priv(sch);
1040        struct qfq_class *cl = (struct qfq_class *)arg;
1041
1042        if (cl->qdisc->q.qlen == 0)
1043                qfq_deactivate_class(q, cl);
1044}
1045
1046static unsigned int qfq_drop(struct Qdisc *sch)
1047{
1048        struct qfq_sched *q = qdisc_priv(sch);
1049        struct qfq_group *grp;
1050        unsigned int i, j, len;
1051
1052        for (i = 0; i <= QFQ_MAX_INDEX; i++) {
1053                grp = &q->groups[i];
1054                for (j = 0; j < QFQ_MAX_SLOTS; j++) {
1055                        struct qfq_class *cl;
1056                        struct hlist_node *n;
1057
1058                        hlist_for_each_entry(cl, n, &grp->slots[j], next) {
1059
1060                                if (!cl->qdisc->ops->drop)
1061                                        continue;
1062
1063                                len = cl->qdisc->ops->drop(cl->qdisc);
1064                                if (len > 0) {
1065                                        sch->q.qlen--;
1066                                        if (!cl->qdisc->q.qlen)
1067                                                qfq_deactivate_class(q, cl);
1068
1069                                        return len;
1070                                }
1071                        }
1072                }
1073        }
1074
1075        return 0;
1076}
1077
1078static int qfq_init_qdisc(struct Qdisc *sch, struct nlattr *opt)
1079{
1080        struct qfq_sched *q = qdisc_priv(sch);
1081        struct qfq_group *grp;
1082        int i, j, err;
1083
1084        err = qdisc_class_hash_init(&q->clhash);
1085        if (err < 0)
1086                return err;
1087
1088        for (i = 0; i <= QFQ_MAX_INDEX; i++) {
1089                grp = &q->groups[i];
1090                grp->index = i;
1091                grp->slot_shift = QFQ_MTU_SHIFT + FRAC_BITS
1092                                   - (QFQ_MAX_INDEX - i);
1093                for (j = 0; j < QFQ_MAX_SLOTS; j++)
1094                        INIT_HLIST_HEAD(&grp->slots[j]);
1095        }
1096
1097        return 0;
1098}
1099
1100static void qfq_reset_qdisc(struct Qdisc *sch)
1101{
1102        struct qfq_sched *q = qdisc_priv(sch);
1103        struct qfq_group *grp;
1104        struct qfq_class *cl;
1105        struct hlist_node *n, *tmp;
1106        unsigned int i, j;
1107
1108        for (i = 0; i <= QFQ_MAX_INDEX; i++) {
1109                grp = &q->groups[i];
1110                for (j = 0; j < QFQ_MAX_SLOTS; j++) {
1111                        hlist_for_each_entry_safe(cl, n, tmp,
1112                                                  &grp->slots[j], next) {
1113                                qfq_deactivate_class(q, cl);
1114                        }
1115                }
1116        }
1117
1118        for (i = 0; i < q->clhash.hashsize; i++) {
1119                hlist_for_each_entry(cl, n, &q->clhash.hash[i], common.hnode)
1120                        qdisc_reset(cl->qdisc);
1121        }
1122        sch->q.qlen = 0;
1123}
1124
1125static void qfq_destroy_qdisc(struct Qdisc *sch)
1126{
1127        struct qfq_sched *q = qdisc_priv(sch);
1128        struct qfq_class *cl;
1129        struct hlist_node *n, *next;
1130        unsigned int i;
1131
1132        tcf_destroy_chain(&q->filter_list);
1133
1134        for (i = 0; i < q->clhash.hashsize; i++) {
1135                hlist_for_each_entry_safe(cl, n, next, &q->clhash.hash[i],
1136                                          common.hnode) {
1137                        qfq_destroy_class(sch, cl);
1138                }
1139        }
1140        qdisc_class_hash_destroy(&q->clhash);
1141}
1142
1143static const struct Qdisc_class_ops qfq_class_ops = {
1144        .change         = qfq_change_class,
1145        .delete         = qfq_delete_class,
1146        .get            = qfq_get_class,
1147        .put            = qfq_put_class,
1148        .tcf_chain      = qfq_tcf_chain,
1149        .bind_tcf       = qfq_bind_tcf,
1150        .unbind_tcf     = qfq_unbind_tcf,
1151        .graft          = qfq_graft_class,
1152        .leaf           = qfq_class_leaf,
1153        .qlen_notify    = qfq_qlen_notify,
1154        .dump           = qfq_dump_class,
1155        .dump_stats     = qfq_dump_class_stats,
1156        .walk           = qfq_walk,
1157};
1158
1159static struct Qdisc_ops qfq_qdisc_ops __read_mostly = {
1160        .cl_ops         = &qfq_class_ops,
1161        .id             = "qfq",
1162        .priv_size      = sizeof(struct qfq_sched),
1163        .enqueue        = qfq_enqueue,
1164        .dequeue        = qfq_dequeue,
1165        .peek           = qdisc_peek_dequeued,
1166        .drop           = qfq_drop,
1167        .init           = qfq_init_qdisc,
1168        .reset          = qfq_reset_qdisc,
1169        .destroy        = qfq_destroy_qdisc,
1170        .owner          = THIS_MODULE,
1171};
1172
1173static int __init qfq_init(void)
1174{
1175        return register_qdisc(&qfq_qdisc_ops);
1176}
1177
1178static void __exit qfq_exit(void)
1179{
1180        unregister_qdisc(&qfq_qdisc_ops);
1181}
1182
1183module_init(qfq_init);
1184module_exit(qfq_exit);
1185MODULE_LICENSE("GPL");
1186
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